Resonant magnetic switch assembly



May 31 1949- H. G. wElGHTMAN 2,471,594

RESONANT MAGNETIC SWITCH ASSEMBLY Filed Aug. 14, 194s 9 nffa/m/vmfmg- 4 Y INVENTOR. /:IeaEe-r 6. L/E/@f/m/w CBM U. VM

f4 )5/"Hey support in position,

Patented May 31, 1949 RESONANT MAGNETIC SWITCH ASSEMBLY Herbert G. Weightman, Scituate, Mass., assigner, by mesne assignments, to Stevens-Arnold, Inc., Boston, Mass., a corporation of Massachusetts Application August 14, 1946, Serial No. 690,387 4 Claims. (Cl. 200-91) This invention relates to electric switches having resonant armatures which close electric circuits when alternating currents having the frequencies to which their armatures are resonant, are supplied through their energizing coils, and which are known generally, as resonant switches.

Prior resonant switches for performing the duties for which this invention was devised, utilized pairs of resonant armatures supported as cantilever beams from the opposite sides of sealed glass envelopes. Such switches were not only costly but their desired resonant frequencies,

in mass produced switches, were difiicult to maintain.

This invention provides a resonant switch which utilizes but a single resonant armature for each frequency to which the switch is responsive, and which is less expensive and more emcient than the prior switches.

Objects of the invention are to improve the performance of, and to reduce the cost of, resonant switches.

The invention will now be described with reference to the drawing, of which:

Fig. 1 is a plan View looking downwardly upon an assembled switch embodying this invention;

'E l 2 tt ,Lip .i5 to be connected to an electric circuit for closing same when the contact surface Il ofthe armature I4 strikes the contact surface IB of the contact member 9. e

The armature I4 is resonant at a selected frequency which, by way of example, may be 100 cycles per second, and when alternating current of that frequency is passed through the coil I9,

the deflection of the armature will be sumcient Fig. 2 is a plan View similar to Fig. 1 but with a portion of the energizing coil removed;

Fig. 3 is a sectional view along the lines 3--3V of Fig. 2, and

Fig. 4 is a plan view with a portion of the energizing coil removed, of another switch embodying this invention, and having two armatures resonant at different frequencies.

Referring first to Figs. 1, 2 and 3, the metal channel member 5 has the perpendicular extensions 5 with the turned over ears l at one end, which extend over and support in position, the permanent magnet 8 against the contact member 3 of magnetizable metal, and the Wrapper I0 of electric insulation around the magnet and the contact member. The extensions 6 of the channel member 5 have the turned over ears I I at their other end, and which extend over'and the brass filler block I2 against the fixed end I3 of the armature I4 of magnetizable spring metal.

The contact member `3 has a perpendicular extension I5 with the contact surface I8 thereon adjacent and normally spaced from the contact surface -I1 on the adjacent side of the free end of the armature I4 which is seen to be supportedas a cantilever beam.

The coil form I8 is supported on the channel member 5 around the armature I4, and has Wound thereon the energizing coil I3 which is adapted to be conected by the Wires 2.0 to a source of alternating current.

The fixed end I3 of the armature I4, and the outer end of the contact member l9 are adapted to cause the contact surface I1 to strike the contact surface I6.

The armature I4 is magnetized by the current flowing through the coil I9 whereby the free end of the armature will alternately be attracted to and released by, the inner end of the contact member '9. The magnet 8 initially magnetizes the contact member 9 whereby the free end of the armature is attracted thereby when no current is flowing through the energizing coil, thus biasing the free end of the armature towards the contact member. The coil magnetizes the armature to the opposite polarity during the half-cycles the magnetic field of the coil opposes that of the magnet whereby the armature is repelled bythe contact member. During the other half-cycles, the magnetic fields of thecoil` and of the magnet are in aiding relation providing increased attraction between the free end of the armature and the contact member. This provides greater armature movement and more ture during the assembly of the switch, the eiec.

tive stiffness and therefore the resonant frequency of each armature can accurately be adjusted to that desired.

'The resonant switch illustrated by Fig. 4 is similar to that described in connection with Figs. 1-3 except that two armatures 30 and 3lY have corresponding ends anchored in the brass filler block I2 in the channel member 5; the contact member 9 has its inner end 32 extending between the free ends of the armatures 30 and 3| with its contact surface 33 spaced from the contact sury face 34 of the armature 30, and with its contact surface 35 spaced from the contact surface 3-8 of the armature 3|; the planes of the armatures and the contact member are perpendicular in the channel member to those of Figs. 1-3, and one of the wires 2| is connected to the brass block I2 instead of to the fixed end of one of the armatures.

The wires 2l are adapted to connect both armatures 30 and 9i, and the contact member 9 of Fig. 4 to an electric circuit to be closed. The armature Bills seen to be longer than the armature 3| whereby it is resonant at a lower frequency. Thus the electric circuit to which the wires 2| of Fig. 4 are connected, will be closed when current having the frequency to which the armature 30 is resonant, is passed through the coil i9, and when current having the frequency to which the armature 3l is resonant, is passed through the coil. Or if the resonance curves of the two overlap, the circuit to be closed by the switch, will be lclosed at anyfrequency in the band of frequencies covered by the overlapping resonance curves.

An advantage of the embodiment of Fig. 4, in addition to providing two resonant armatures in one switch, is that the two armatures are magnetized alike by their energizing coil resulting in their free ends having the same magnetic poles and thereby repelling each other thusv biasing -them away from the contact member and providing greater armature movement.

Another advantage of the switch of Fig. 4 is that since the magnetic member 9 to which they are attracted and by which they vare repelled when alternating current is supplied to their energizing coil, is between the two armatures, their movements are 180 out of phase, and the vibrations of the switch caused by the motion of one armature are reduced by the oppositely phased motion of the other armature whereby the mass of the block' I2, and of the switch can be substantially reduced. This advantage is so great that it is preferred that even where the switch is intended to AbeV resonant at only one frequency, the two armatures 3,0 andl v3i bev used with the contact surface being omittedv from one.

In such a case both armatures preferably would be resonant atv substantially'the'same frequency.rv

While embodiments of thezinvention have been described for lthe DUIDQSG. ofv illustration, it should be understoodthatthe'V invention vis not limitedI to the exact apparatus'and y'arrangement of apparatus illustrated, l as ymodifications thereof may be suggested by", those skilled 'inA the art without v departure from theessence of the invention; Whatisclaimedisz. y 1. A resonant switch comprisingfra channel member lhaving a' base, ands'idesjextending subthereto and to said armature when alternating current having the resonant frequency of said` armature is passed through said coil.

2. A resonant switch comprising a channel member having a base, and sides extending substantially perpendicular thereto; an armature of magnetizable spring metal having a rst portion contacting said base in one end of said ,memben having a second portion extending substantially perpendicular to'said first portion, and a third portion extending as a' cantilever beam towards the other end of said member; a'iiller block on said first portion having its inner end contacting said second portiom" extensions on said sides bent over against said ller block for supporting same and said armature in said member; a contact member of magnetizable metal in the other end of said member, said contact member having a first portion extending substantially parellel to said base, and having a second, inner portion extending substantially perpendicular to said base and overlapping and spaced from said free end of said armature; a permanent magnet on said iirst portion of said contact member and having its inner end closely spaced from said free end of said armature; insulation around said magnet and said rst portion of said contact member for insulating same from said channel member; other extensions on said sides bent over against said insulation for supporting same, said magnet and contact member in said channel member, and an energizing coil supported around armature is passed through said coil.

3. A resonant switch as claimed in claim 1 in which the fixed end of the armature is anchored in the filler block, and in which another ilexible reed armature of magnetizable metal spaced froni -said armature has one end anchored in said block.

4. A magnetic switchvcomprising a channeled base having spaced, substar tially parallel sides,

f a flexible reed, armature member of magnetizable metal, means for supporting one end of said stantially perpendicular-tosaid base; an armature of magnetizable prin'g @metal means` inm n fone end; of 'said f'jsaiclI channel "end yof 'said armature;

` a permanent magnet alongside saidfcontact mem-YK ber and having its innerendcloselyspaced from said free end of said armature; insulation around v said contactr member` andsaidmagnet forv insulating samer from'. said channel member; extensions on said sides of said channel member bent over at one end thereof for supporting said filler block and said armature in said channelv .member; other extensions on said sides bent over at the other end thereof for supporting said insulation, said magnet and said contact member in said channel member, and an energizing coil supported around said channel member for magnetizing said armature, said free end of saidv armature being adapted to strike said contact member and to close an electric circuit connected r11115.!!uirting""said arma.-I

innerl end overlapping le of this patent:y

member in one end of said base, said means including extensions from said sides bent over towards each other substantially perpendicular to .said sides, a contact member of magnetizable Y metal having one end overlapping the other end .of said karmature member, means for' supporting ember of., mag.. L y 2 the other end of said contact member in the other e`nd of said base, saidlast mentioned means including extensions from said sides bent over to'- Ywards each other substantially perpendicular to said sides, means insulating one of said members from said base, said base being of metal, and an energizing coil supported around said base.

HERBERT G'. WEIGHTMAN.

REFERENCES CITED l The following references are Aof record in the UNITED STATES PATENTS Number Name Date 684,378 Potter Oct. 8, 1901 708,539 Fell Sept. 9, 1902 996,713 Hartmann-Kempf July 4, 1911 1,088,771 Dean Mar. 3, 1914 Marrison May 1, 1945 

